Method of driving mask stage and method of mask alignment

ABSTRACT

In a scanning-type projection exposure system, curvature of a movable mirror that is used to measure mask stage coordinate positions is determined while the mask stage is moved in the scanning direction, by measuring coordinate positions, perpendicular to the scan direction, of the mask stage and of a mask mark elongated in the scan direction. The results of the measurements are used for correcting or compensating positional deviation during scanning. Rotational deviation of a mask pattern area is determined and is corrected or compensated. Also, a mask is aligned with respect to a coordinate system of the mask stage as pre-processing for exposure, using a mask alignment mark having two crossing linear patterns and determining a coordinate position of the crossing point by moving the mask relative to an observation area.

This is a continuation of Ser. No. 08/966,353 filed Nov. 7, 1997, nowabandoned, which is a Reissue No. of 08/217,841 filed Mar. 25, 1994,U.S. Pat. No. 4,464,715.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of driving a mask stage and amethod of mask alignment. More particularly, the present inventionrelates to a method of driving a stage, which is suitably applied to acase where a reticle-side stage is driven in a scan direction in aslit-scan exposure type projection exposure apparatus, and a method ofmask alignment in the projection exposure apparatus.

2. Related Background Art

When a semiconductor element, a liquid crystal display element, a thinfilm magnetic head, or the like is manufactured in a photolithographyprocess, a projection exposure apparatus for transferring a pattern on aphotomask or a reticle (to be generally referred to as a “reticle”hereinafter) onto a substrate (a wafer, glass plate, or the like) coatedwith a photosensitive material is used.

As a conventional projection exposure apparatus, a step-and-repeat typereduction projection exposure apparatus (stepper) for sequentiallyexposing a pattern image on a reticle onto each of shot areas bysequentially moving the shot areas of a wafer into an exposure field ofa projection optical system is popularly used.

In recent years, since patterns on semiconductor devices or the liketend to be miniaturized, it is required to increase the resolution of aprojection optical system. For this reason, in order to increase theresolution, a technique for decreasing the wavelength of exposure light,a technique for increasing the numerical aperture of the projectionoptical system, and the like have been examined. However, with eithertechnique, it becomes difficult to maintain high accuracy of imagingperformance (a distortion, curvature of field, and the like) on theentire exposure field when an exposure field as large as that in theprior art is to be assured. For this reason, an apparatus which iscurrently reconsidered its use is a so-called slit-scan exposure typeprojection exposure apparatus.

In the slit-scan exposure type projection exposure apparatus, a patternon a reticle is exposed onto a wafer, wherein the reticle and wafer arebeing synchronously scanned relative to a rectangular or arcuatedillumination area (to be referred to as a “slit-like illumination area”hereinafter).

Therefore, when a pattern with the same area as that in the steppersystem is to be exposed onto a wafer, the exposure field of theprojection optical system in the slit-scan exposure system can be set tobe smaller than that in the stepper system. As a result, accuracy ofimaging performance in the exposure field may be improved.

The mainstream of the conventional reticle size is 6″, and themainstream of the projection magnification of the projection opticalsystem is x⅕. However, as the area of the circuit pattern of, e.g., asemiconductor element increases, the 6 ″ reticle cannot serve itspurpose at the x⅕ magnification. For this reason, a projection exposureapparatus in which the projection magnification of the projectionoptical system is changed to, e.g., x¼ must be designed. In order tocope with such an increase in area of a pattern to be transferred, theslit-scan exposure system is advantageous.

In a projection exposure apparatus of this type (stepper), a reticlemust be aligned in advance on a reticle stage. For this purpose, areticle alignment device is arranged on a reticle mark on the reticle.Such a reticle alignment device is disclosed in U.S. Pat. No. 4,710,029.In an alignment system disclosed in U.S. Pat. No. 4,710,029, lightreflected by an alignment mark on a reticle is incident on a sensor viaa vibration mirror and a slit. When the output from the sensor issynchronously detected by a driving signal of the vibration mirror, theposition of the alignment mark relative to a slit is detected. Theposition of the alignment mark is detected based on a signal from thesensor in the alignment system, and the reticle is moved by a servosystem, so that the alignment mark accurately coincides with the slit.As a result, alignment of the reticle with respect to the apparatus mainbody is executed.

SUMMARY OF THE INVENTION

In such a slit-scan exposure system, when the moving path of the reticlestage for driving a reticle is curved with respect to a desired path(for example, the moving path has a predetermined curvature with respectto a desired linear path), each shot area on a wafer undesirably has anintra-shot distortion according to the curve (curvature) of the movingpath of the reticle stage. Furthermore, when the characteristics of anintra-shot distortion vary from one exposure apparatus to another, sucha variation results in a matching error between different layers on thewafer. When the reticle stage is controlled by a method of measuring theposition of the reticle stage by interfering light components reflectedby a stationary mirror and a movable mirror provided to the reticlestage using an optical interferometer, such a curve of the path of thereticle stage is caused by a curve of the movable mirror.

The present invention has been made in consideration of the abovesituation, and has as its object to provide a method of driving a stage,which can prevent generation of an intra-shot distortion even when amovable mirror provided to a stage at the side of reticle (mask) has acurve in a slit-scan exposure type exposure apparatus.

In order to achieve the above object, according to the first invention,there is provided a method of driving a mask stage using the mask stagewhich mounts a mask formed with a predetermined pattern and is movablein a predetermined scan direction, a movable mirror which is arranged onthe mask stage and has a reflection surface substantially parallel tothe scan direction, measurement means for measuring a coordinateposition, in a direction perpendicular to the scan direction, of themask stage by radiating a measurement beam into the movable mirror, asubstrate stage which mounts a photosensitive substrate and is movablein a direction substantially parallel to the scan direction, anillumination system for illuminating a predetermined area on the maskwith illumination light, a projection optical system for projecting thepattern on the mask onto the photosensitive substrate, and an exposuredevice for sequentially exposing the pattern on the mask onto thephotosensitive substrate while synchronously scanning the mask stage andthe substrate stage in the scan direction with respect to an opticalaxis of the projection optical system, comprising:

the first step of placing the mask on the mask stage;

the second step of calculating a curved amount of the movable mirror bymeasuring the coordinate position, in the direction perpendicular to thescan direction, of the mask stage by the measurement means whilescanning the mask stage in the scan direction; and

the third step of moving the mask stage in the direction perpendicularto the scan direction to correct the curved amount of the movable mirrorcalculated in the second step when the mask stage is scanned in the scandirection with respect to the optical axis.

According to the second invention, there is provided a method of drivinga mask stage using a mask guide which is formed with a guide portionextending in predetermined scan direction, the mask stage which ismounted on the mask. Guide to be movable in the scan direction, andmounts a mask formed with a predetermined pattern, a movable mirrorwhich is attached to the mask stage, and has a reflection surfacesubstantially parallel to the scan direction, measurement means formeasuring a coordinate position, in a direction perpendicular to thescan direction, of the mask stage by radiating a measurement beam intothe movable mirror, a substrate stage which is movable in the directionsubstantially parallel to the scan direction and mounts a photosensitivesubstrate, an illumination system for illuminating a predetermined areaon the mask with illumination light, a projection optical system forprojecting the pattern on the mask onto the photosensitive substrate,and an exposure device for sequentially exposing the pattern on the maskonto the photosensitive substrate while synchronously scanning the maskstage and the substrate stage in the scan direction with respect to anoptical axis of the projection optical system, comprising the steps of:

calculating a curved amount of the movable mirror by measuring thecoordinate position, in the direction perpendicular to the scandirection, of the mask stage by the measurement means by scanning themask stage in the scan direction with reference to the mask guide; and

moving the mask stage in the direction perpendicular to the scandirection so as to correct the curved amount of the movable mirror whena transfer mask is scanned via the mask stage in the scan direction withrespect to the predetermined shaped illumination area.

According to the first invention, since the curved amount of the movablemirror is measured with reference to the measurement mark provided tothe mask, and the measured curved amount is corrected in exposure, evenwhen the movable mirror provided to the mask stage on the side of themask has a curve, generation of an intra-shot distortion at thesubstrate side can be prevented.

According to the second invention, since the curved amount of themovable mirror is measured with reference to the mask guide, when thestraightness of the mask guide is good, the curve amount of the movablemirror can be quickly and easily measured, and the measured curvedamount can be corrected in exposure.

In the slit-scan exposure type projection exposure apparatus as well,when a reticle is exchanged with another one, the new reticle must bealigned. However, in the slit-scan exposure system for driving a reticlein a predetermined direction with high accuracy during exposure, areticle interferometer for monitoring the position of the reticle withhigh accuracy must be mounted. For this reason, it is difficult toassure larger driving strokes of the reticle in the X and Y directionsand the rotational direction than those in a conventional stepper typeprojection exposure apparatus upon alignment of a reticle. Therefore, itis difficult to directly apply an alignment method used in theconventional stepper to the slit-scan exposure type projection exposureapparatus.

In general, the electron beam drawing error of a reticle mark withrespect to the outer shape of a reticle is about ±0.5 mm to ±1 mm. Inthis case, when the reticle is aligned on the reticle stage withreference to its outer shape, if a pattern drawing area is inclined at amaximum inclination angle with respect to the outer shape of thereticle, the lateral shift amount of a laser beam from a reticleinterferometer exceeds an allowable value of the lateral shift amount ina receiver of the interferometer. Therefore, it is difficult tocompletely correct the drawing error of a reticle in the conventionalalignment method without causing a measurement error of the reticleinterferometer.

Furthermore, an apparatus which mounts such a reticle interferometer canalign a reticle at an arbitrary position with high accuracy by open-loopcontrol. For this reason, an alignment method which can detect theposition of a reticle mark at high speed by open-loop control must bedeveloped in place of conventional closed-loop control (servo control)based on synchronous detection.

The present invention has been made in consideration of the abovesituation, and has as its object to provide an alignment method whichcan align a reticle (mark) at high speed with high accuracy in aslit-scan exposure type projection exposure apparatus.

In order to achieve the above object, according to the third invention,there is provided a method of aligning a mask with respect to acoordinate system on the side of a mask stage as pre-processing forexposing a pattern on the mask onto a photosensitive substrate using themask stage which mounts the mask formed with a predetermined pattern andis movable in a predetermined scan direction, a substrate stage whichmounts the photosensitive substrate and is movable in a directionsubstantially parallel to the scan direction, an illumination system forilluminating a predetermined illumination area on the mask withillumination light, a projection optical system for projecting thepattern on the mask onto the photosensitive substrate, observation meansfor observing a mark on the mask, and an exposure device forsequentially exposing the pattern on the mask onto the photosensitivesubstrate while synchronously scanning the mask stage and the substratestage in the scan direction with respect to an optical axis of theprojection optical system, comprising:

the first step of placing, as the mask, a mask formed with a firstalignment mark having two linear patterns which cross each other, on themask stage;

the second step of moving the two linear patterns in a direction tocross each other on the first alignment mark on the mask relative to anobservation area of the observation means;

the third step of calculating a coordinate position, in the coordinatesystem on the side of the mask stage, of a crossing point of the twolinear patterns of the first alignment mark by processing image dataobtained by the observation means; and

the fourth step of aligning the mask to the coordinate system on theside of the mask stage on the basis of the coordinate position of thecrossing point of the two linear patterns of the first alignment mark.

According to the fourth invention, there is provided a method ofaligning a mask with respect to a coordinate system on the side of amask stage as pre-processing for exposing a pattern on the mask onto aphotosensitive substrate using the mask stage which mounts the maskformed with a predetermined pattern and is movable in a predeterminedscan direction, a substrate stage which mounts the photosensitivesubstrate and is movable in a direction substantially parallel to thescan direction, an illumination system for illuminating a predeterminedillumination area on the mask with illumination light, a projectionoptical system for projecting the pattern on the mask onto thephotosensitive substrate, and an exposure device for sequentiallyexposing the pattern on the mask onto the photosensitive substrate whilesynchronizing scanning the mask stage and the substrate stage in thescan direction with respect to an optical axis of the projection opticalsystem, comprising:

the first step of placing, as the mask, a mask formed with an alignmentmark, on the mask stage; and

the second step of calculating a rotational angle of the mask withrespect to the coordinate system on the side of the mask stage bycalculating a coordinate position of the alignment mark, and when therotational angle calculated in the second step exceeds a predeterminedallowable value, the method further comprising:

the third step of unloading the mask from the mask stage;

the fourth of rotating the mask stage by a predetermined rotationalangle in a direction of the rotational angle calculated in the secondstep; and

the fifth stage of placing the mask on the mask stage again, androtating the mask stage in a direction opposite to the rotationaldirection in the fourth step.

According to the fifth invention, there is provided a method of aligninga mask with respect to a coordinate system on the side of a mask stageas pre-processing for exposing a pattern on the mask onto aphotosensitive substrate using the mask stage which mounts the maskformed with a predetermined pattern and is movable in a predeterminedscan direction, a substrate stage which mounts the photosensitivesubstrate and is movable in a direction substantially parallel to thescan direction, an illumination system for illuminating a predeterminedillumination area on the mask with illumination light, a projectionoptical system for projecting the pattern on the mask onto thephotosensitive substrate, and an exposure device for sequentiallyexposing the pattern on the mask onto the photosensitive substrate whilesynchronously scanning the mask stage and the substrate stage in thescan direction with respect to an optical axis of the projection opticalsystem, comprising:

the first step of placing, as the mask, a mask formed with an alignmentmark, on the mask stage; and

the second step of calculating a rotational angle of the mask withrespect to the coordinate system on the side of the mask stage bycalculating a coordinate position of the alignment mark, and when therotational angle calculated in the second step exceeds a predeterminedallowable value, the method further comprising:

the third step of rotating the mask stage in a direction opposite to therotational angle calculated in the second step;

the fourth step of unloading the mask from the mask stage; and

the fifth stage of rotating the mask stage in a direction opposite tothe rotational direction in the third step, and placing the mask on themask stage again.

According to the third invention, when the mask stage is driven withrespect to the observation area of the observation means so as toobliquely scan the mask, the coordinate position of the crossing pointof the two linear patterns of the alignment mark on the mask can bemeasured by the open-loop control. Therefore, mask alignment can berealized at high speed with high accuracy.

According to the fourth and fifth inventions, when a mask is re-placedon the mask stage upon occurrence of a rotation error of the mask whichposes a problem when a slit-scan exposure type mask stage is used, maskalignment can be realized at high speed with high accuracy. Also,strokes of the reticle stage upon alignment need not be increased, andlength measuring means need not have any correction mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a projection exposure apparatusaccording to an embodiment of the present invention;

FIG. 2A is a plan view showing the arrangement of a curve measurementmark and an alignment mark on a reticle;

FIG. 2B is a plan view showing the arrangement of the alignment mark andthe like on an area conjugate with the effective field of a projectionoptical system;

FIG. 2C is an enlarged view showing fine alignment marks 29A to 30D;

FIG. 3A is a plan view of a stage on the side of a wafer;

FIG. 3B is a plan view of a stage on the side of a reticle;

FIG. 4A is a projection view showing the mark arrangement on a reticle;

FIG. 4B is a plan view showing the arrangement of reference marks on areference mark plate 6;

FIG. 4C is an enlarged view showing an example of a reference mark 35E(or 36E);

FIG. 5 is a partially cutaway schematic view showing the arrangement ofa reticle alignment microscope 19 and an illumination system;

FIG. 6A is a view showing an image observed by an image pickup elementshown in FIG. 5; FIG. 6B is a waveform chart showing an image signal inthe X direction corresponding to the image shown in FIG. 6A;

FIGS. 7A to 7D are waveform charts showing a curve which is obtained byapproximately measurement values upon measurement of the curve of amovable mirror, and image signals corresponding to respective portion ofthe movable mirror;

FIG. 8A is a plan view showing a reticle 12 of the embodiment;

FIG. 8B is an enlarged view showing a linear pattern 28c of a curvemeasurement mark 28 in FIG. 8A;

FIG. 8C is an enlarged view showing another example of the curvemeasurement mark;

FIG. 8D is an enlarged view showing still another example of the curvemeasurement mark;

FIG. 9 is a schematic view showing another example of a reticlealignment microscope;

FIG. 10A is a plan view showing of the curve of movable mirror on theside of a reticle stage in a slit scan exposure type projection exposureapparatus;

FIG. 10B is an enlarged view showing a distortion generated in a shotarea formed on a wafer due to the curve of the movable mirror;

FIG. 10C is a plan view showing the arrangement of shot areas on thewafer;

FIG. 11 is a perspective view showing a reticle loader system;

FIG. 12A is a plan view showing the arrangement of alignment marks on areticle;

FIG. 12B is a plan view showing the arrangement of alignment marks andthe like on an area conjugate with the effective field of a projectionoptical system;

FIG. 12C is an enlarged view showing fine alignment marks 29A to 30A;

FIGS. 13A, 13B, 13C, 13D, 13E, and 13F are waveform charts showingvarious image pickup signals obtained from an image pickup element uponexecution of rough alignment of a reticle;

FIG. 14A is an optical path chart showing the state of a laser beambetween an interferometer for the x-axis on the side of a reticle stageand a movable mirror 21x;

FIG. 14B is an optical path chart showing a case whererin the movablemirror 21X is rotated from the state shown in FIG. 14A; and

FIGS. 15A, 15B, 15C, 15D, and 15E are views for explaining an operationfor re-placing a reticle 12 by rotating a reticle fine driving state 11when a pattern drawing area PA on the reticle 12 inclined with respectto a reticle coordinate system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a projection exposure method according to the presentinvention will be described below with reference to the accompanyingdrawings. In this embodiment, the present invention is applied to a casewherein a pattern on a reticle is exposed onto a wafer using a slit-scanexposure type projection exposure apparatus.

FIG. 1 shows a projection exposure apparatus of this embodiment.Referring to FIG. 1, a pattern on a reticle 12 is illumination withexposure light EL from an illumination optical system ILS. Theillumination optical system ILS forms a rectangular illumination area(to be referred to as a “slit-like illumination area” hereinafter) bythe exposure light EL on the reticle 12. The reticle pattern and thesurface of a wafer 5 are optically conjugate with each other withrespect to a projection optical system 8. A reticle pattern image of theslit-like illumination area is projected and exposed onto the wafer 5via the projection optical system 8.

In this case, the wafer 5 is scanned at a constant velocity V/β (1/β isthe reduction factor of the projection optical system 8) in the backwarddirection with respect to the plane of the drawing of FIG. 1 (in thebackward direction with respect to the plane of the drawing in theY-axis) in synchronism with the reticle 12 which is scanned relative tothe slit-like illumination area of the exposure light EL at a constantvelocity V in the forward direction with respect to the plane of thedrawing of FIG. 1 (in the forward direction with respect to the plane ofthe drawing in the Y-axis).

Driving systems of the reticle 12 and the wafer 5 will be describedbelow.

A reticle Y-driving stage 10, which is movable in the Y-axis direction(the direction perpendicular to the plane of the drawing of FIG. 1) ismounted on a reticle support table 9. A reticle fine driving stage 11 ismounted on the reticle Y-driving stage 10. The reticle 12 is held by,e.g., a vacuum chuck on the reticle fine driving stage 11. The reticlefine driving stage 11 is finely movable in the X direction parallel tothe plane of the drawing of FIG. 1 in a plane perpendicular to theoptical axis of the projection optical system 8, the Y directionperpendicular to the plane of the drawing, and the rotational direction(8 direction) in the X-Y plane. The reticle fine driving stage 11performs position control of the reticle 12 in the X, Y, and θ directionby a very small amount with high accuracy.

A movable mirror 21 is arranged on the reticle fine driving stage 11.

An interferometer 14 arranged on the article support table 9 radiates alaser beam onto the movable mirror 21, and always monitors thepositions, in the X, Y, and 8 directions, of the reticle fine drivingstage 11 on the basis of light reflected by the movable mirror.

Position information S1 obtained by the interferometer 14 is supplied toa main control system 22A.

On the other hand, a wafer Y-axis driving stage 2, which is movable inthe Y-axis direction, is mounted on a wafer support table 1. A waferX-axis driving stage 3, which is movable in the X-axis direction, ismounted on the wafer Y-axis driving stage 2. A Zθ-axis driving stage 4is arranged on the wafer X-axis driving stage 3. The wafer 5 is held onthe ZS-axis driving stage 4 by vacuum chucking.

A movable mirror 7 is also fixed on the Zθ-axis driving stage 4, and thepositions, in the X, Y and θ directions, of the Zθ-axis driving stage 4are monitored by an interferometer 13 which is arranged outside theapparatus. Position information obtained by the interferometer 13 isalso supplied to the main control system 22A. The main control system22A controls the alignment operations of the wafer Y-axis driving stage2 to the Zθ-axis driving stage 4 via a wafer driving device 22B and thelike, and also controls the operations of the entire apparatus.

As will be described later, a reference or fiducial mark plate 6 isfixed on the Zθ-axis driving stage 4 so as to attain a correspondencebetween a wafer coordinate system and a reticle coordinate system. Thereference mark plate 6 is arranged near the wafer 5. The wafercoordinate system is defined by coordinates measured by theinterferometer 13 on the wafer side, and the reticle coordinate systemis defined by coordinates measured by the interferometer 14 on thereticle side. Various reference marks are formed on the reference markplate 6, as will be described later. These reference marks include aluminous reference mark. The luminous reference mark is a reference markilluminated from the back side with illumination light guided to theZθ-axis driving stage 4 side.

Reticle alignment microscopes 19 and 20 for simultaneously observing thereference marks on the reference mark plate 6 and marks on the reticle12 are equipped above the reticle 12 of this embodiment.

In this case, deflection mirrors 15 and 16 for guiding detection lightfrom the reticle 12 to the reticle alignment microscopes 19 and 20 arearranged. The deflection mirrors 15 and 16 are movable in the Xdirection. When the exposure sequence is started, the deflection mirrors15 and 16 are respectively retreated from the exposure light EL bymirror driving devices 17 and 18 in accordance with an instruction fromthe main control system 22A.

Furthermore, an off-axis alignment device 34 for observating alignmentmarks (wafer marks) on the wafer 5 is arranged on the side surfaceportion, in the Y direction, of the projection optical system 8.

The mechanism and operation for performing alignment of the reticle 12and measurement of the curve of the movable mirror (to be describedlater) will be described below.

FIG. 2A shows the arrangement of alignment marks (reticle marks) andcurve measurement marks on the reticle 12, and FIG. 2B shows a slit-likeillumination area 32 and the like in an area 33R conjugate with theeffective exposure field of the projection optical system on thereticle. Assume that the scan direction is defined as a y direction, anda direction perpendicular to the y direction is defined as an xdirection. Referring to FIG. 2A, a light-shielding portion 31 is formedaround a pattern area of a central portion on the reticle 12. Marksformed outside the light-shielding portion 31 are classified into curvemeasurement marks 27 and 28, and fine alignment marks 29A, 29B, 29C,29D, 30A, 30B, 30C, and 30D. The curve measurement mark 27 on the rightside is defined by a linear pattern 27c elongated along the y directionas the scan direction, and cross patterns formed at the two end portionsof the linear pattern. The curve measurement mark 28 on the left side isdefined to have a linear pattern 28c symmetrical with that of the curvemeasurement mark 27 on the right side.

As will be described later, the curve measurement marks 27 and 28 ofthis embodiment can also be used as alignment marks upon execution ofcoarse alignment (rough alignment) of the reticle 12, i.e., as rouchsearch alignment marks.

The fine alignment marks 29A and 29B are formed between alight-shielding portion 31R on the right side and one cross pattern ofthe curve measurement mark 27 so as to be close to each other in the ydirection, and the fine alignment marks 29C and 29D are formed betweenthe light-shielding portion 31R on the right side and the other crosspattern of the curve measurement mark 27 so as to be close to each otherin the y direction. The fine alignment marks 30A to 30D are formed onthe left side to be symmetrical with these fine alignments marks 29A to29D. Each of these fine alignment marks 29A to 29D and 30A to 30D isdefined by arranging two sets of three linear patterns at apredetermined interval in the x direction, and arranging two sets ofthree linear patterns at a predetermined interval in the y direction, asshown in FIG. 2C.

Upon execution of rough alignment of the reticle 12 in this embodiment,the cross patterns of the curve measurement mark 28 on the left side inFIG. 2A are detected by the reticle alignment microscope (to be referredto as an “RA microscope” hereinafter) 20 in FIG. 1. Thereafter, thecross patterns of the curve measurement mark 27 are moved to theobservation area of the RA microscope 19, and the position of thealignment mark 27 is similarly measured. In this case, a pattern-freeportion of the reference mark plate 6 in FIG. 1 is moved into theexposure field of the projection optical system 8, and is illuminatedfrom its bottom portion. In this manner, the curve measurement marks 27and 28 are illuminated from their rear surface side with illuminationlight emerging from the reference mark plate 6.

In the above-mentioned sequence, the positions of the cross patterns ofthe curve measurement marks 27 and 28 with respect to the RA microscopes19 and 20 in FIG. 1 can be obtained. More specifically, the positionalrelationship between the reticle 12 and the reticle coordinate systemcan be roughly determined in the above mentioned sequence. A roughcorrespondence between the RA microscopes 19 and 20 and the wafercoordinate system can be attained by measuring the reference marks onthe reference mark plate 6 in FIG. 1 by the RA microscopes 19 and 20.Thus, rough alignment that can avoid an overlap between the finealignment marks 29A to 29D and 30A to 30D and the reference marks on thereference mark plate 6 is completed. A mark search sequence in the roughalignment will be described later.

The curve measurement sequence for the movable mirror and the finealignment sequence will be described below. Prior to the description ofthese sequences, the detailed arrangement of the wafer stage and thereticle stage will be explained.

FIG. 3A is a plan view of the wafer stage. Referring to FIG. 3A, thewafer 5 and the reference mark plate 6 are arranged on the Zθ-axisdriving stage 4. An X-axis movable mirror 7X and a Y-axis movable mirror7Y are fixed on the Zθ-axis driving stage 4. On the wafer 5, a slit-likeillumination area 32W corresponding to the slit-like illumination area32 in FIG. 2B is illuminated with exposure light, and observation areas19W and 20W are respectively conjugate with observation areas 19R and20R in FIG. 2B.

Laser beam LWX and LW_(of) which are separated by an interval IL areradiated onto the movable mirror 7X along optical paths which areparallel to the X-axis and respectively pass the optical axis of theprojection optical system and the reference point of the alignmentdevice 34, and two laser beams LWY1 and LWY2 which are separated by theinterval IL are radiated onto the movable mirror 7Y along optical pathsparallel to the Y axis. In exposure, the coordinate value measured by aninterferometer using the laser beam LWX is used as the X-coordinate ofthe Zθ-axis driving stage 4, and an average value (Y₁+Y₂) of coordinatevalues Y₁ and Y₂ measured by interferometers which respectively use thelaser beams LWY1 and LWY2 is used as the Y coordinate. The rotationalamount of the Zθ-axis driving stage in the rotational direction (θdirection) is measured based on e.g., the difference between thecoordinate values Y₁ and Y₂. Based on these coordinates, the position,on the X-Y plane, and the rotational angle of the Zθ-axis driving stage4 are controlled.

In particular, in the Y direction as the scan direction deterioration ofaccuracy caused by, e.g., an inclination upon scanning is preventedusing the average value of the measurement results from the twointerferometers. On the other hand, the position in the X-axis directionwhen the off-axis alignment device 34 is used is controlled based on themeasurement value from a special-purpose interferometer using the letterbeam LW_(of) so as to not cause a so-called Abbe's error.

FIG. 3B is a plan view of the reticle stage. Referring to FIG. 3B, thereticle fine driving stage 11 is mounted on the reticle Y-driving stage10, and the reticle 12 is held thereon. An x-axis movable mirror 21x andtwo y-axis movable mirrors 21y1 and 21y2 are fixed to the reticle finedriving stage 11. Laser beams LRx are radiated onto the movable mirror21x in a direction parallel to the x-axis, and laser beams LRy1 and LRy2are radiated onto the movable mirrors 21y1 and 21y2 in a directionparallel to the y-axis.

As in the wafer stage, the coordinate, in the y direction, of thereticle fine driving stage 11 adopts an average value (y₁+y₂)/2 ofcoordinate values y₁ and y₂ measured by two interferometers using thelaser beams LRy1 and LRy2.

Also, a coordinate value measured by an interferometer 14x using the twolaser beams LRx in the x direction is used. At this time, an averagevalue of the coordinate values measured using the two laser beams may beused, or the coordinate value may be obtained using either one laserbeam LRx. In addition, the rotational amount, in the rotationaldirection (θ direction), of the reticle fine driving stage is measuredbased on e.g., the difference between the coordinate values y₁ and Y₂.

In this case, as the movable mirrors 21y1 and 21y2 for the y directionas the scan direction, corner cube type reflection members are used. Thelaser beams LRy1 and LRy2 reflected by the movable mirrors 21y1 and 21y2are respectively reflected by reflection mirrors 39 and 38, and arereturned. More specifically, the interferometers for the reticle aredouble-pass interferometers, thereby preventing positional shifts of thelaser beams upon rotation of the reticle fine driving stage 11. Notethat the X-axis interferometer 14x may comprise a double-passinterferometer.

As in the wafer stage, the slit-like illumination area 32 and theobservation areas 19R and 20R of the RA microscopes 19 and 20 arearranged on the reticle 12. The reticle 12 and the ZS-axis driving stage4 in FIG. 3A can be observed from only the observation areas 19R and20R.

The curve of the movable mirror 21x is measured by measuring therelationship between the reticle 12 and the Zθ-axis driving stage 4, asdescribed above, and alignment accuracy in exposure and rotationalaccuracy of the reticle 12 and wafer 5 can be improved.

FIG. 4A shows a reticle image 12W obtained by projecting the reticle 12shown in FIG. 2A onto the reference mark plate 6 shown in FIG. 3A. FIG.4A illustrates mark images 29AW to 29DW conjugate with the finealignment marks 29A to 29D in FIG. 2A, and mark images 30AW to 30DWconjugate with the fine alignment marks 30A to 30D. Furthermore, FIG. 4Aillustrates mark images 27W and 28W conjugate with the curve measurementmarks 27 and 28.

FIG. 4B shows the arrangement of reference marks on the reference markplate 6. On the reference mark plate 6 in FIG. 4C, reference marks 35Eand 36E are formed to be separated by the same interval, in the Xdirection, as that between the mark images 27W and 28W in FIG. 4A. Thereference mark 35E is defined by two linear patterns of light-shieldingportions arranged at a predetermined interval in the X direction, asshown in FIG. 4C, and the same applies to the reference mark 36E. Thesereference marks 35E and 36E are illuminated with illumination light ofthe same wavelength as that of the exposure light from the rear surfaceside.

Also, on the reference mark plate 6, reference marks 35A to 35D and 36Aare formed to have substantially the same arrangement as that of themark images 29AW to 29DW and 30AW to 30DW in FIG. 4A. These referencemarks are illuminated with illumination light of the same wavelength asthat of the exposure light from the rear surface of the reference markplate 6. On the reference mark plate 6, a reference mark 37A is formedat a position separated by an interval IL in the Y direction as the scandirection from the middle point between the reference marks 35A and 36A.The interval IL is equal to a base line amount as an interval betweenthe reference point in an image field of the projection optical system 8and the reference point of the off-axis alignment device 34 in FIG. 1.Similarly, reference marks 37B, 37C, and 37D are respectively formed atpositions separated by the interval IL in the Y direction from themiddle point between the reference marks 35B and 36B, the middle pointbetween the reference marks 35C and 36C, and the middle point betweenthe reference marks 35D and 36D.

Then, reticle 12 is finally aligned by measuring the positionalrelationship between the fine alignment marks 29A to 29D and thecorresponding reference marks 35A to 35D using the RA microscope 19, andmeasuring the positional relationship between the fine alignment marks30A to 30D and the corresponding reference marks 36A to 36D using the RAmicroscope 20.

Upon measurement of the curve of the movable mirror 21x, the positionalshift amount between the reference mark 35E (or 36E) in FIG. 4B and thelinear pattern 27c (or the linear pattern 28c) of the curve measurementmark 27 on the side of the reticle 12 in FIGS. 2A is detected by the RAmicroscope 19 (or the RA microscope 20).

The arrangement of the RA microscope 19 and the like shown in FIG. 1will be described in detail below for the purpose of explaining themethod of obtaining the positional shift amount.

FIG. 5 shows the RA microscope 19 and its illumination system. Referringto FIG. 5, illumination light EL of the same wavelength as that of theexposure light is guided from a portion outside the Zθ-axis drivingstage 4 to the interior of the Zθ-axis during stage 4 via an opticalfiber 44. In place of the optical fiber 44, the exposure light may berelayed by a lens system. The illumination light guided in this mannerilluminates the reference marks 35A to 35D on the reference mark plate 6via a lens 45A, a beam splitter 45B, and a lens 45C, and theillumination light transmitted through the beam splitter 45B illuminatesthe reference marks 36A to 36D on the reference mark plate 6 via lenses45D and 45E, a mirror 45F, and a lens 45G. The illumination light canalso illuminate the reference marks 35E and 36E.

For example, light transmitted through the reference mark 35E forms animage of the reference mark 35E on the linear pattern 27c on the reticle12 via the projection optical system 8. Light from the optical image ofthe reference mark 35E and the linear pattern 27c reaches a half mirror42 via a deflection mirror 15, and lenses 40A and 40B. The light issplit into two light beams by the half mirror 42, and the two lightbeams are respectively incident on the image pickup surfaces of x- andy-axis image pickup elements 43X and 43Y, each comprising atwo-dimensional CCD. Of these image pickup elements, on an image pickupscreen 43Xa of the image pickup element 43X, the image of the referencepattern 27c and an image 35ER of the reference mark 35E are projected,as shown in FIG. 6A. In this case, the direction of the horizontal scanline of the image pickup screen 43Xa of the x-axis image pickup element43X corresponds to the x direction, and the direction of the horizontalscan line of the image pickup screen of the y-axis image pickup element43Y corresponds to the y direction.

Therefore, the positional shift amount, in the x direction between theimage 35ER of the reference mark 35E and the linear pattern 27c can becalculated from an additive mean of an image pickup signal S4X from theimage pickup element 43X. The image pickup signal S4X is supplied to asignal processing device 41. The image pickup signal S4X is detected tobe a digital signal by analog/digital conversion in the signalprocessing device 41. Image data on respective scan lines are added andaveraged on the. X-axis in the signal processing device 41, and theimage signal S4X on the X-axis as the additive mean is as shown in FIG.6B. These image data are respectively processed as one-dimensional imageprocessing signals. On FIG. 6B, the abscissa of the image signal S4Xcorresponds to time t. However, when the width of the image pickupscreen of the image pickup element 43X is measured in advance, theabscissa can be regarded to plot a position x.

When the signal obtained as described above is subjected to arithmeticprocessing in the signal processing device 41, a position x₃ in the xdirection corresponding to the image of the linear pattern 27c of thereticle 12 in FIG. 6A, a position x₁ corresponding to the left patternof the image 35ER of the reference mark 35E, and a position x₂corresponding to the right pattern of the image 35ER can be obtained. Arelative positional shift amount Δx, in the x direction, between thelinear pattern 27c and the reference mark 35E is given by:

Δx=x₃−(x₁+x₂)/2   (1)

In this manner, the positional shift amount, in the x direction betweenthe linear pattern 27c of the curve measurement mark 27 in FIG. 2A andthe projected image of the reference mark 35E in FIG. 4B can beobtained. Similarly, the positional shift amount, in the x direction,between the linear pattern 28c of the curve measurement mark 28 in FIG.2A and the projected image of the reference mark 36E in FIG. 4B can beobtained using the RA microscope 20.

Examples of a method of measuring the curved amount of the reflectionsurface of the movable mirror 21x on the reticle stage side in FIG. 3Busing these potential shift amounts will be described below.

The first method of measuring the curve of the movable mirror 21x is amethod executed with reference to the linear pattern 27c (or the linearpattern 28c) of the curve measurement mark 27 in FIG. 2A. Morespecifically, in this case, in a state wherein the image of thereference mark 35E and the linear pattern 27c are observed by the RAmicroscope 19 to monitor the positional shift amount Δx in the xdirection therebetween, as shown in FIG. 5, and in a state wherein themeasurement value of the x-axis interferometer 14x on the reticle sidein FIG. 3B is maintained to be a constant value, the reticle finedriving stage 11 is moved in the y direction as the scan direction.Then, positional shift amounts Δx_(i), in the x direction, between theimage of the reference mark 35E and the linear pattern 27c arecalculated at a large number of measurement positions y_(i) in the ydirection.

FIG. 7A shows the results of plotting the positional shift amountsΔx_(i) at the measurement positions y_(i), a line 70 is a straight linewhich extends straight in the y direction, and curve 71 is obtained byapproximating a series of sampling points (points with marks x in FIG.7A). In the measurement data as the basis of the curve 71, a positionalshift amount Δx₁ from the straight line 70 is calculated to be thepositional shift amount, in the x direction, between a middle point 72of the image 35ER of the reference pattern 35E and the linear pattern27c in the image pickup signal S4X, as shown in FIG. 7B. Similarly,positional shift amounts Δx_(n) and Δx_(m) are respectively calculatedfrom image pickup signals shown in FIGS. 7C and 7D. FIGS. 7B to 7D showimage pickup signals from the image pickup element 43X. The samplinginterval in the y direction is determined by the curvature to becalculated, and the measurement accuracy of the RA microscope 19 as analignment sensor.

The respective relative positional shift amounts Δx_(i) are measuredalong the curve of the movable mirror 21x, as indicated by the marks xin FIG. 7A.

Upon calculation of the curve 71, filtering is executed in a softwaremanner in accordance with a variation of the positional shift amountsΔx_(i). A function corresponding to the calculated curve 71 isapproximately by a quadratic curve as a function of the position y. Forexample, a coefficient A of the term of y² of the approximated functionis calculated, and when the reticle fine driving stage 11 is scanned inthe y direction in slit-scan exposure, the reticle fine driving state 11is finely driven in the x direction in accordance with the position inthe y direction so as to cancel the curve of the movable mirror 21x. Inthis manner, an intra-shot distortion of a pattern image exposed ontoeach shot area of the wafer 5 can be eliminated.

Referring to FIG. 7A, the curve 71 may be divided at proper intervals inthe y direction, and the respective curve sections may be linearlyapproximated to obtain a coefficient B at each position y. Correctionmay then be performed on the basis of the coefficient B in the slit-scanexposure.

When image sampling is performed, in order to average reticle drawingerrors, additive mean values in the vertical direction may be calculatedfor scan lines on the entire image pickup screen. Alternatively,sampling may be performed while scanning the reticle 12, and the sampledvalues may be averaged.

In the above-mentioned embodiment, the reticle fine driving stage 11 isscanned in the y direction while maintaining the measurement value, inthe x direction, of the x-axis interferomenter 14x to be a predeterminedvalue. Conversely, the reticle fine driving stage 11 may be scanned inthe y direction while the linear pattern 27c is set at the middle pointof the image 35ER of the reference mark 35E in FIG. 6A. In this case,the positional shift amount Δx measured by the RA microscope 19 isalways 0, and the measurement value, in the x direction, of the x-axisinterferometer 14x directly represents the curved amount of the movablemirror 21x.

In the projection exposure apparatus, when heat is accumulated due toexposure light radiated onto the pattern formation surface of thereticle 12 in exposure, and a temperature change of the reticle stageitself (the reticle fine driving stage 11) occurs, the curved state ofthe movable mirror 21x may change. However, a temperature sensor or thelike may be arranged on the reticle stage to measure the relationshipbetween the temperature change amount and the change in curved state inadvance, and the correction coefficient may be varied in accordance withthe measurement result, thereby canceling the change in curved state.Furthermore, after the curve correction of the movable mirror 21x, whenanother reticle is set and the same measurement is performed in the x-and y-axes, reticle drawing errors at the respective positions can bemeasured. Since the reticle drawing error between adjacent patternportions is small, reticle drawing errors from a position near the curvemeasurement mark to the pattern portion are assumed to be almost thesame and are grouped, and the error group may be corrected in slit-scanexposure, thus allowing reticle drawing error correction.

FIG. 10A shows a case wherein the movable mirror 21x on the reticlestage is curved. If the reflection surface of the movable mirror 21x isparallel to the straight line 70 which is perfectly parallel to they-axis, the pattern on the reticle 12 can be exposed on the waferwithout any distortion by scanning the reticle fine driving stage 11 inthe y direction in a state wherein the x coordinate measured by thelaser beam LRx is maintained to be a predetermined value.

However, when the reflection surface of the movable mirror 21x is curvedto have a maximum shift amount Δx in the x direction, as indicated by asolid curve in FIG. 10A, it is controlled to maintain the position, onthe reflection surface, of the laser beam LRx from the interferometer tobe the position of the straight line 70 indicated by a broken line uponscanning of the reticle 12. Therefore, the reticle fine driving stage 11is driven along a curved path in a direction opposite to the curve ofthe movable mirror 21x. As a result, as shown in FIG. 10B, each shotarea 78 on the wafer has an intra-shot distortion according to thecurvature of the moving path of the reticle fine driving stage 11. Asshown in FIG. 10C, the intra-shot distortion is common to all shot areas79 on the wafer 5. In this case, if the characteristics of theintra-shot distortion vary among exposure apparatuses, such a variationresults in a matching error between different layers on the wafer.

As described above, when the reticle fine driving stage 11 is scanned inthe y direction in slit-scan exposure, the reticle fine driving stage 11is finely driven in the x direction in accordance with the position inthe y direction so as to cancel the curve of the movable mirror 21x.Thus, the intra-shot distortion of the pattern image exposed onto eachshot area is eliminated, and a matching error between different layerson the wafer can also be eliminated.

In the above-mentioned embodiment, the curve measurement marks 27 and 28shown in FIG. 8A are used as curve measurement marks, and for example,the linear pattern 28c (see FIG. 8B) of the curve measurement mark 28 isused as a reference upon measurement of the curve of the movable mirror.However, as a reference used upon measurement of the curve of themovable mirror, a multi-pattern 73 which is defined by aligning linearpatterns, extending in the y direction, in the x direction at apredetermined interval, as shown in FIG. 8C, may be used. When themulti-pattern 73 is used, and the measurement results of the linearpatterns are averaged in the x direction, the curved amount of themovable mirror can be measured with higher accuracy. Also, as areference used upon measurement of the curve of the movable mirror, amulti-line-and-space pattern 74, which is defined by aligningline-and-space patterns, formed at a predetermined pitch the ydirection, in the x direction at a predetermined interval, as shown inFIG. 8D, may be used. The multi-line-and-space pattern 74 can be easilyformed on, e.g., a reticle by an electron beam drawing device or thelike.

In the above-mentioned embodiment, the positional shift amounts of thelinear patterns 27c and 28c are calculated with reference to thereference marks 35E and 36E formed on the reference mark plate 6 on thewafer side. Alternatively, these reference marks may be arranged in theRA microscope.

FIG. 9 shows an RA microscope which comprises internal reference marks.Referring to FIG. 9, illumination light from the linear pattern 27c onthe reticle 12 is reflected by the half mirror 15, and forms an image ofthe linear pattern 27c on an index plate 75 via lenses 40C and 49D. Anindex mark 76 defined by linear patterns aligned at a predeterminedinterval in a direction conjugate with the x direction on the reticle 12is formed on the index plate 75, and illumination light passing throughthe index plate 75 reaches the half mirror 42 via a mirror 77 and lenses40D and 40E. The light is split into two light beams by the half mirror42, and these two beams are respectively incident on the image pickupsurfaces of the x- and y-axis image pickup elements 43X and 43Y. Otherarrangements are the same as those in the RA microscope 19 shown in FIG.5.

In the RA microscope shown in FIG. 9, the positional shift amount of thelinear pattern 27c is detected with reference to the index mark 76.Therefore, upon measurement of the curve of the movable mirror 21x, thereference mark plate 6 on the wafer side need not be used.

In the above-mentioned embodiment, the curve measurement marks 27 and 28are used. However, in FIG. 3B, if the straightness of the movement, inthe y direction, of the reticle fine driving stage 11 is good, when themeasurement values in the x direction are monitored by the x-axisinterferometer 14x while the reticle fine driving stage 11 is simplyscanned in the y direction, the measurement values directly representthe curved amount of the movable mirror 21x.

Next, a sequence from loading of the wafer 5 and the reticle 12 to theend of alignment in the projection exposure apparatus of this embodimentwill be explained below. First, the reticle 12 is pre-aligned withreference to its outer shape on a reticle loader (to be describedlater).

FIG. 11 shows a reticle loader system for loading the reticle 12 ontothe reticle fine driving stage 11 shown in FIG. 1. The reticle loadershown in FIG. 11 is constituted by two reticle arms 23A and 23B, an armrotation shaft 25 coupled to these reticle arms 23A and 23B, and arotation mechanism 26 for rotating the arm rotation shaft 25. Vacuumchucking grooves 24A and 24B are respectively formed on the reticleplacing surfaces of the reticle arms 23A and 23B, and the reticle arms23A and 23B are supported to be independently rotatable via the armrotation shaft 25.

Upon loading of the reticle 12, the reticle 12 is transferred fromanother reticle convey mechanism (not shown) onto the reticle arm 23A ata position A3. In this case, the other reticle arm 23B is used forunloading the reticle used in the previous process. Then, the reticle 12is aligned to predetermined accuracy on the reticle arm 23A withreference to its outer shape by a reticle outer shape pre-alignmentmechanism arranged near the position A3, and thereafter, the reticle 12is vacuum-chucked on the reticle arm 23A. The reticle outer shapepre-alignment mechanism is disclosed in, e.g., FIG. 7 of U.S. Pat. No.4,716,299, although not shown in FIG. 11. The rotation mechanism 26rotates the reticle arm 23A via the arm rotation shaft 25 to convey thereticle 12 to a position B3 in the Y direction (in the direction of thereticle fine driving stage 11 in FIG. 1).

At this time, since the vacuum chucking groove 24A is located at aposition in the direction perpendicular to the chucking position on thereticle fine driving stage 11 and outside the pattern area of thereticle 12, the reticle arm 23A can freely load/unload the reticle 12onto the reticle fine driving stage 11 in a state wherein the reticlefine driving stage 11 is moved to a front portion in the y direction asthe scan direction. When the reticle 12 has reached a position above thereticle fine driving stage 11 (see FIG. 1), the arm rotation shaft 25 ismoved downward in the −Z direction. Then, the reticle 12 is placed onthe vacuum chucking surface on the reticle fine driving stage 11, andthe reticle arm 23A retreats after the end of transfer of the reticle12. Thereafter, the reticle fine driving stage 11 conveys the reticle 12in the direction of a position C3. In this case, the reticle arms 23Aand 23B are independently driven to respectively perform, e.g., reticleloading and unloading operations at the same time, thus increasing thereticle exchange speed.

Then, alignment of the reticle 12 is performed, and a mechanism andoperation therefor will be described below. As described above, roughalignment of the reticle 12 can be performed using the curve measurementmarks 27 and 28. Thus, the rough alignment mechanism and operation usingthe curve measurement marks (rough search alignment marks) 27 and 28will be described in detail below, partially repeating theabove-mentioned description.

After the reticle 12 is placed on the reticle fine driving stage 11, thecurve measurement mark (rough search alignment mark) 28 on the left sidein FIG. 2A is detected by the RA microscope 20 in FIG. 1. FIG. 2B showsthe observation areas 19R and 20R, on the reticle 12, of the RAmicroscopes 19 and 20 in this case. Upon execution of rough search ofthe reticle 12, the curve measurement marks (rough search alignmentmarks) 27 and 28 are respectively located outside the observation areas19R and 20R and outside the area 33R conjugate with the effectiveexposure field. Although the curve measurement marks (rough searchalignment marks) 27 and 28 must have a large size for rough search, ifthe size of the exposure field of the projection optical system isincreased accordingly, this results in an increase in cost. Thus, aprocedure upon execution of rough search in this embodiment will bedescribed below with reference to FIGS. 12A and 12B.

FIG. 12A is an enlarged view showing a portion near one cross pattern ofthe curve measurement mark (rough search alignment mark) 28, and FIG.12B shows FIG. 12A in the reduced scale. Referring to FIGS. 12A and 12B,the widths, in the x and y directions, of a square effective field20R_(ef) of the RA microscope 20 are represented by W, and the designvalue of a sum of a drawing error and a setting error of a pattern withrespect to the outer shape of the reticle 12 is represented by ΔR.Therefore, as shown in FIG. 12B, a square area having the width ΔRalways includes a crossing point 28a of one cross pattern of the curvemeasurement mark (rough search alignment mark) 28. An object to bedetected is the x- and y-coordinates of the crossing point 28a of thecross pattern. In this embodiment, the reticle 12 is stepped via thereticle fine driving stage 11 in a direction that crosses, at 45°, thetwo straight lines passing the crossing point 28a of the curvemeasurement mark (alignment mark) 28, thereby scanning the effectivefield 20R_(ef) having the width W relative to a position near thecrossing point 28a obliquely with respect to the x- and y-axes. Uponexecution of the oblique scanning, the x- and y-coordinates of thecrossing point 28a are obtained as those of the reticle fine drivingstage 11 when the two straight lines passing the crossing point 28across reference point in the effective field 20R_(ef).

For this purpose, if the integral part of a positive real number a isexpressed by INT(a), the number of search frames as the minimum numberof times of scanning the square area having the width ΔR with theeffective field 20R_(ef) having the width W is given by {INT(ΔR/W)+1}.The number of search frames is calculated in advance. Then,{INT(ΔR/W)+1} effective fields AS, BS, C5, . . . each having the width Ware set in a square area having the width ΔR and including the effectivefield B5 (FIG. 12B) at substantially the central position, so that theedge portions of the effective areas slightly overlap each other in the45° direction with respect to the x- and y-axes. The reticle finedriving stage 11 (FIG. 1) is driven by the stepping method under theopen-loop control, and an image in each effective field is sampled whilesetting each effective field in the effective field 20R_(ef) in FIG. 12Ain turn.

As shown in FIG. 12B, the crossing point 28a of the curve measurementmark (alignment mark) 28 to be searched is present within at least aΔR×ΔR wide search range, and the curve measurement mark (alignment mark)28 is sufficiently larger than the search range. Therefore, as can beunderstood from the above description, when the effective field isstepped in the oblique direction with respect to curve measurement mark(alignment mark) 28, the coordinates of the crossing point 28a of thecurve measurement mark (alignment mark) 28 can be detected by theminimum number of frames. Image processing at that time can beone-dimensional image processing for an image signal obtained by addingall scan lines in the pickup frame.

FIGS. 13A to 13F show various image signals obtained by adding all scanlines. FIGS. 13A and 13D show image signals along the x and y directionsobtained in the effective field A5 in FIG. 12B, FIGS. 13B and 13E showimage signals along the x and y directions obtained in the effectivefield B5 in FIG. 12B, and FIGS. 13C and 13F show image signals along thex and y directions obtained in the effective field C5 in FIG. 12B. Thex-coordinate of the crossing point 28a is calculated from the imagesignal shown in FIG. 13B, and the y-coordinate of the crossing point 28ais calculated from the image signal shown in FIG. 13F. Similarly, the RAmicroscope 20 detects the x- and y-coordinates of a crossing point 28bof the other cross pattern of the curve measurement mark (alignmentmark) 28 shown in FIG. 2A.

After the two-dimensional coordinate positions of the crossing points28a and 28b of the cross patterns at the two ends of the curvemeasurement mark (alignment mark) 28 are detected, as described above,the curve measurement mark (alignment mark 27) is, in turn, moved to theobservation area of the RA microscope 19, and the two-dimensionalcoordinate positions of the crossing points 27a and 27b of the crosspatterns at the two ends of the curve measurement mark (alignment mark)27 are similarly detected. In this case, a pattern-free portion of thereference mark plate 6 in FIG. 1 is moved into the exposure field of theprojection optical system 8, and is illuminated from its bottom portion.In this manner, the curve measurement marks 27 and 28 are illuminatedfrom their rear surface side with illumination light emerging from thereference mark plate 6.

In the above-mentioned sequence, the positional relationship of thecurve measurement marks (alignment marks) 27 and 28 with respect to theobservation areas 19R and 20R of the RA microscopes 19 and 20 in FIG.2B, and a rough positional relationship of the curve measurement marks(alignment marks) 27 and 28 with respect to the reticle coordinatesystem can be obtained. A rough correspondence between the observationareas 19R and 20R of the RA microscopes and the wafer coordinate systemcan be attained by measuring the reference marks on the reference markplate 6 (FIG. 1) using the RA microscopes 19 and 20. Thus, roughalignment that can avoid an overlap between the fine alignment marks 29Ato 29D and 30A to 30D and the reference marks (35A to 35D and 36A to36D) on the reference mark plate 6 in FIG. 4B is completed.

In this embodiment, in order to reduce the lens diameter of theprojection optical system 8, alignment marks on the reticle 12 areclassified into the curve measurement marks (alignment marks) and finealignment marks. However, when the projection optical system 8 can havea large lens diameter, these curve measurement marks (alignment marks)and fine alignment marks can be common marks. In this case as well, thetechnique for searching the curve measurement marks (alignment marks) bystepping the stage in the oblique direction (FIGS. 12A and 12B) can beadopted, and the RA microscopes 19 and 20 can simultaneously search thecurve measurement marks (alignment marks).

The allowable value of a rotational angle when the reticle 12 of thisembodiment is placed on the reticle fine driving stage 11 will beexamined below. For this purpose, the arrangement of an interferometerfor measuring the coordinate, in the x direction, of the reticle finedriving stage 11 on which the reticle 12 is placed, as shown in FIG. 3B,will be partially described in detail below with references to FIGS. 14Aand 14B.

As shown in FIG. 14A, the x-axis interferometer (not shown in FIGS. 14Aand 14B) radiates a laser beam LRx of p-polarized light onto apolarization beam splitter 100. The laser beam LRx is transmittedthrough a junction surface 100a of the polarized beam splitter 100a,passes through a quaterwave plate 101, and is then incident on thex-axis movable mirror 21x in a state of circularly polarized light. Thelaser beam LRx reflected by the movable mirror 21x is reflected by thejunction surface 100a of the polarization beam.splitter 100 via aquaterwave plate 71 in a state of s-polarized light, and propagatestoward a corner cube 102. The laser beam LRx reflected by the cornercube 102 is reflected by the junction surface 100a of the polarizationbeam splitter 100, and is incident on the movable mirror 21x in a stateof circularly polarized light via the quaterwave plate 101.

Thereafter, the laser beam LRx reflected by the movable mirror 21x isincident on the junction surface 100a of the polarization beam splitter100 in a state of p-polarized light via the quaterwave plate 71, and thelaser beam LRx transmitted through the junction surface 100a is returnedto a receiver of the x-axis interferometer (not shown). Morespecifically, when the movable mirror 21x is displayed by Δx in the xdirection, since the optical path length of the laser beam LRx changesby 4·Δx, the x-axis interferometer on the reticle side also serves as adouble-pass interferometer. In this case, if the interval, in the ydirection, between the middle point in the y direction between the laserbeam LRx emerging from the interferometer and the laser beam LRxreturned to the interferometer, and the vertex of the corner cube 102 isrepresented by La, and the interval, in the x direction, from themovable mirror 21x to the vertex of the corner cube 102 is representedby Lb, a distance L_(T) of the path of the laser beam LRx after thelaser beam LRx is reflected by the movable mirror 21x until the laserbeam LRx passes through the junction surface 100a of the polarizationbeam splitter is given by the following equation:

L_(T)=La+Lb   (2)

In this case, as shown in FIG. 14B, when the reflection surface of themovable mirror 21x is largely rotated at an an angle θ about an axisperpendicular to the plane of the drawing of FIG. 14B with respect to aplane perpendicular to the incident laser beam LRx, the position, in they direction, of the laser beam LRx returned to the interferometerlaterally shifted by an interval ΔL from a case wherein the angel θ is0. The interval ΔL can be expressed as follows using the above-mentioneddistance L_(T):

ΔL=4·L_(T)·θ  (3)

Therefore, when the rotational angle θ of the movable mirror 21x exceedsan allowable value θ₁, the lateral shift amount ΔL of the laser beam LRxincident on the receiver of the interferometer exceeds a predeterminedallowable amount. Thus, a reference beam and the laser beam LRx forlength measurement can no longer sufficiently overlap each other,resulting in a length measurement error of the interferometer. In thiscase, the allowable value θ₁ of the rotational angle which does notcause an interferometer error is calculated in advance, and the rotationerror of the reticle 12 must be controlled not to exceed the calculatedallowable value θ₁ upon execution of rough alignment of the reticle 12.The movable mirror 21x is rotated when the pattern drawing area on thereticle 12 has been rotated with respect to the reticle coordinatesystem defined by the measurement value of the interferometer on thereticle side and when the reticle fine driving stage 11 is rotated in adirection to cancel the rotational angle of the pattern drawing area.Therefore, in order to control the rotational angle θ of the movablemirror 21x to be equal to or smaller than the allowable value θ₁, therotational angle of the pattern drawing area on the reticle 12 must becontrolled to be equal to or smaller than the allowable value θ₁ uponexecution of rough alignment of the reticle 12.

In this embodiment, when the reticle 12 is placed on the reticle finedriving stage 11, the rotational angle of the pattern drawing area onthe reticle 12 is controlled to be equal to or smaller than theallowable value θ₁. The technique for attaining this control will bedescribed below with reference to FIGS. 15A, 15B, 15C, 15D, and 15E.

As shown in FIG. 15A, in an initial state of reticle loading, thereticle 12 is aligned with reference to its outer shape, and isvacuum-chucked on the reticle arm 23A. For the sake of descriptiveconvenience, a pattern drawing area PA is largely inclined with respectto the outer shape of the reticle 12. In this case, the x-axis isassumed in a direction parallel to the laser beam LRx in FIG. 3B, they-axis is assumed in a direction parallel to the laser beams LRy1 andLRy2, and the reticle coordinate system is formed by these x- andy-axes. The inclination of the drawing area PA is expressed by thecrossing angle between a straight line passing the two crossing points27a and 27b at the two ends of one curve measurement mark (rough searchalignment mark) 27 (or a straight line passing the two crossing points28a and 28b at the two ends of the other curve measurement mark (roughsearch alignment mark) 28), and the y-axis of the reticle coordinatesystem. In this initial state, an x_(RS)-axis and a y_(Rs)-axis areassumed on the reticle fine driving stage 11 to be parallel to the x-and y-axes, respectively.

Subsequently, as shown in FIG. 15B, after the reticle 12 is placed onthe reticle fine driving stage 11 by the reticle arm 23A, the reticlearm 23A is escaped to the position B3. In this state, theabove-mentioned rough alignment is executed for the alignment marks 27and 28, and a rotation angle (rotation error) φ of the drawing area PAon the reticle 12 with respect to the y-axis of the reticle coordinatesystem is measured. The rotational angle φ₁ is obtained to be, e.g., anangle defined between a straight line connecting the crossing points 27aand 27b at the two ends of the alignment mark 27, and the y-axis. Forthe purpose of descriptive convenience, assume that the drawing area PAis rotated clockwise with respect to the y-axis.

When the rotational angle φ₁ exceeds the allowable value θ₁, the reticle12 is temporarily detached from the reticle fine driving state 11 usingthe reticle arm 23A, as shown in FIG. 15C. Then, the reticle finedriving stage 11 is rotated by a mechanical limit angle φ₂ of therotational angle in the direction of the rotational angle φ₁. Morespecifically, the y_(Rs)-axis on the reticle fine driving stage 11 isrotated clockwise by the limit angle φ₂ with respect to the y-axis.Thereafter, as shown in FIG. 15D, the reticle 12 is attached on thereticle fine driving stage 11 again using the reticle arm 23A. Thereticle fine driving stage 11 is then rotated counterclockwise by thelimit angle φ₂ with respect to the y-axis, and is restored to theoriginal position. Thus, as shown in FIG. 15E, the angle of the drawingarea PA of the reticle 12 with respect to the y-axis of the reticlecoordinate system becomes smaller than the allowable value θ₁.

When the angle of the drawing area PA of the reticle 12 with respect tothe y-axis of the reticle coordinate system exceeds the allowable valueθ₁ even in the state shown in FIG. 15E, the operations shown in FIGS.15C to 15E can be repeated again. By the operation for rotating thereticle fine driving stage 11 by one revolution, the rotation error ofeven a reticle which has a rotation error twice the allowable value θ₁can be suppressed to be equal to or smaller than the allowable value θ₁.Furthermore, when the operation for rotating the reticle fine drivingstage 11, and restoring the stage 11 to an original position is repeatedn times (n is an integer equal to or larger than 2), the rotation errorof the drawing area PA on the reticle 12 can be suppressed to be equalto or smaller than the allowable value θ₁ regardless of the magnitude ofthe rotation error in the initial state of the reticle 12. Thereafter,the above-mentioned fine alignment is executed, thus completing thealignment of the reticle 12.

When the rotational angle φ₁ of the drawing area PA on the reticle 12satisfies θ₁<φ₁≦φ₂, the reticle fine driving stage 11 may be rotated bythe rotational angle φ₁ of the drawing area PA in place of being rotatedby the mechanical limit angle φ₂.

As described above, in this embodiment, since the positions of reticlemarks are detected using the image processing system while stepping thereticle 12 in an obligue direction, measurement upon execution of roughalignment of a reticle in the slit-scan exposure type projectionexposure apparatus can be realized. Furthermore, in this embodiment, theimage processing system for fine alignment is also used for roughalignment, and a servo control system required in a synchronousdetection type alignment system like that described in U.S. Pat. No.4,710,029 is omitted. Thus, the arrangement is simplified, and themanufacturing cost can be reduced. When the rotational angle of thedrawing area on the reticle 12 exceeds an allowable value, the reticle12 is detached from the reticle fine driving stage 11, and after thereticle fine driving stage 11 is rotated, the reticle 12 is attachedagain. Since this sequence is adopted, a failure in reticle alignmentcan be avoided.

In the above-mentioned embodiment, as shown in FIGS. 15B and 15C, afterthe reticle 12 is detached from the reticle fine driving stage 11, thereticle fine driving stage 11 is rotated by the rotational angle φ₂.Alternatively, after the reticle fine driving stage 11 is rotated inadvance by −φ₂, the reticle 12 may be detached. In this case, as anoperation corresponding to FIGS. 15D and 15E, after the reticle finedriving stage 11 is rotated by the rotational angle φ₂ to restore anoriginal state, the reticle 12 is attached again onto the reticle finedriving stage 11. With this method as well, the rotational angle of thedrawing area on the reticle 12 can be controlled to be equal to orsmaller than the allowable value.

In the above-mentioned embodiment, as shown in FIGS. 15A to 15E, whenthe rotational angle of the pattern drawing area PA on the reticle 12with respect to the reticle coordinate system exceeds the allowablevalue, the reticle fine driving stage 11 is rotated. Alternatively, thereticle 12 may be rotated in a direction opposite to the rotationalangel by the reticle arm 23A side from which the reticle 12 is detached.For this purpose, a rotation mechanism for rotating the article 12 onthe reticle arm 23A may be added.

Also, for a reticle having a reticle drawing error of the same tendencywith respect to the outer shape reference, a rotation error caused bythe reticle drawing error may be stored, and the reticle fine drivingstage 11 may be driven in the direction of an axis defined by therotation error. Thus, the reticle need not be re-placed on the reticlefine driving stage 11. Furthermore, a tracking error caused by shiftingthe movable mirror 21x in a non-scan direction in slit-scan exposure dueto the rotation error can be decreased.

As described above, the present invention is not limited to theabove-mentioned embodiment, and may adopt various arrangements withinthe spirit and scope of the invention.

What is claimed is:
 1. A method of driving a mask stage using anexposure device having said mask stage which mounts a mask formed with apredetermined pattern and is movable in a predetermined scan direction,a movable mirror which is arranged on said mask stage and has areflection surface substantially parallel to the scan direction,measurement means for measuring a coordinate position, in a directionperpendicular to the scan direction, of said mask stage by radiating ameasurement beam onto said movable mirror, a substrate stage whichmounts a photosensitive substrate and is movable in a directionsubstantially parallel to the scan direction, an illumination system forilluminating a predetermined area on the mask with illumination light,and a projection optical system for projecting the pattern on the maskonto the photosensitive substrate. said exposure device for sequentiallyexposing the pattern on the mask onto the photosensitive substrate whilesynchronously scanning said mask stage and said substrate stage in thescan direction with respect to an optical axis of said projectionoptical system, comprising the steps of: the first step of placing themask on said mask stage; the second step of calculating a curved amountof said movable mirror by measuring the coordinate position, in thedirection perpendicular to the scan direction, of said mask stage bysaid measurement means while scanning said mask stage in the scandirection; and the third step of moving said mask stage in the directionperpendicular to the scan direction to correct the curved amount of saidmovable mirror calculated in the second step when said mask stage isscanned in the scan direction with respect to the optical axis; whereinthe mask has a measurement mark, and the second step includes the stepof calculating the curved amount of said movable mirror with referenceto the measurement mark.
 2. A method of driving a mask stage using anexposure device having said mask stage which mounts a mask formed with apredetermined pattern and is movable in a predetermined scan direction,a movable mirror which is arranged on said mask stage and has areflection surface substantially parallel to the scan direction,measurement means for measuring a coordinate position, in a directionperpendicular to the scan direction, of said mask stage by radiating ameasurement beam onto said movable mirror, a substrate stage whichmounts a photosensitive substrate and is movable in a directionsubstantially parallel to the scan direction, an illumination system forilluminating a predetermined area on the mask with illumination light,and a projection optical system for projecting the pattern on the maskonto the photosensitive substrate, said exposure device for sequentiallyexposing the pattern on the mask onto the photosensitive substrate whilesynchronously scanning said mask stage and said substrate stage in thescan direction with respect to an optical axis of said projectionoptical system, comprising the steps of: the first step of placing themask on said mask stage; the second step of calculating a curved amountof said movable mirror by measuring the coordinate position, in thedirection perpendicular to the scan direction, of said mask stage bysaid measurement means while scanning said mask stage in the scandirection; and the third step of moving said mask stage in the directionperpendicular to the scan direction to correct the curved amount of saidmovable mirror calculated in the second step when said mask stage isscanned in the scan direction with respect to the optical axis; whereinthe mask has a measurement mark, and the second step includes the stepof scanning said mask stage while the measurement mark is aligned to areference position, and calculating the curved amount of said movablemirror on the basis of the coordinate position, in the directionperpendicular to the scan direction, of said mask stage measured by saidmeasurement means.
 3. A method of aligning a mask with respect to acoordinate system on the side of a mask stage as pre-processing forexposing a pattern on the mask onto a photosensitive substrate using anexposure device having said mask stage which mounts the mask formed witha predetermined pattern and is movable in a predetermined scandirection, a substrate stage which mounts the photosensitive substrateand is movable in a direction substantially parallel to the scandirection, an illumination system for illuminating a predeterminedillumination area on the mask with illumination light, a projectionoptical system for projecting the pattern on the mask onto thephotosensitive substrate, and observation means for observing a mark onthe mask, the exposure device for sequentially exposing the pattern onthe mask onto the photosensitive substrate while synchronously scanningsaid mask stage and said substrate stage in the scan direction withrespect to an optical axis of said projection optical system,comprising: the first step of placing, as the mask, a mask formed with afirst alignment mark having two linear patterns which cross each other,on said mask stage; the second step of moving the two linear patterns ina direction to cross each other on the first alignment mark on the maskrelative to an observation area of said observation means in a directionwhich is transverse to each of the two linear patterns; the third stepof calculating a coordinate position, in the coordinate system on theside of said mask stage, of a crossing point of the two linear patternsof the first alignment mark by processing image data obtained by saidobservation means; and the fourth step of aligning the mask to thecoordinate system on the side of said mask stage on the basis of thecoordinate position of the crossing point of the two linear patterns ofthe first alignment mark.
 4. A method according to claim 3, wherein themask has a second alignment mark having two linear patterns which crosseach other, at a position different from the first alignment mark; saidmethod further comprises: the fifth step of moving the two linearpatterns in a direction to cross each other on the second alignment markon the mask relative to an observation area of said observation means ina direction which is transverse to each of the two linear patterns, andthe sixth step of calculating a coordinate position, in the coordinatesystem on the side of said mask stage, of a crossing point of the twolinear patterns of the second alignment mark by processing image dataobtained by said observation means; and the fifth step comprises thestep of aligning the mask to the coordinate system on the side of saidmask stage on the basis of the coordinate position of the crossing pointof the two linear patterns of the first alignment mark and thecoordinate position of the crossing point of the two linear patterns ofthe second alignment mark.
 5. A method of aligning a mask with respectto a coordinate system on the side of a mask stage as pre-processing forexposing a pattern on the mask onto a photosensitive substrate using anexposure device having said mask stage which mounts the mask formed witha predetermined pattern and is movable in a predetermined scandirection, a substrate stage which mounts the photosensitive substrateand is movable in a direction substantially parallel to the scandirection, an illumination system for illuminating a predeterminedillumination area on the mask with illumination light, and a projectionoptical system for projecting the pattern on the mask onto thephotosensitive substrate, said exposure device for sequentially exposingthe pattern on the mask onto the photosensitive substrate whilesynchronously scanning said mask stage and said substrate stage in thescan direction with respect to an optical axis of said projectionoptical system, comprising: the first step of placing, as the mask, amask formed with an alignment mark, on said mask stage; and the secondstep of calculating a rotational angle of the mask with respect to thecoordinate system on the side of said mask stage by calculating acoordinate position of said alignment mark, and when the rotationalangle calculated in the second step exceeds a predetermined allowablevalue, said method further comprising: the third step of unloading themask from said mask stage; the fourth step of rotating said mask stageby a predetermined rotational angle in a direction of the rotationalangle calculated in the second step; and the fifth stage of placing themask on said mask stage again, and rotating said mask stage in adirection opposite to the rotational direction in the forth step.
 6. Amethod of aligning a mask with respect to a coordinate system on theside of a mask stage as pre-processing for exposing a pattern on themask onto a photosensitive substrate using an exposure device havingsaid mask stage which mounts the mask formed with a predeterminedpattern and is movable in a predetermined scan direction, a substratestage which mounts the photosensitive substrate and is movable in adirection substantially parallel to the scan direction, an illuminationsystem for illuminating a predetermined illumination area on the maskwith illumination light, and a projection optical system for projectingthe pattern on the mask onto the photosensitive substrate, said exposuredevice for sequentially exposing the pattern on the mask onto thephotosensitive substrate while synchronously scanning said mask stageand said substrate stage in the scan direction with respect to anoptical axis of said projection optical system, comprising: the firststep of placing, as the mask, a mask formed with an alignment mark, onsaid mask stage; and the second step of calculating a rotational angleof the mask with respect to the coordinate system on the side of saidmask stage by calculating a coordinate position of said alignment mark,and when the rotational angle calculated in the second step exceeds apredetermined allowable value, said method further comprising: the thirdstep of rotating said mask stage in a direction opposite to therotational angle calculated in the second step; the fourth step ofunloading the mask from said mask stage; and the fifth step of rotatingsaid mask stage in a direction opposite to the rotational direction inthe third step, and placing the mask on said mask stage again.
 7. Amethod of driving a mask when a mask stage carrying a mask having apredetermined pattern and a mark for a measurement and a substrate stagecarrying a substrate are synchronously moved, comprising the steps of:measuring a positional deviation of said mask stage along a directionperpendicular to a movement direction, by moving said mask stage alongthe movement direction while measuring a position of said mask stagealong the direction substantially perpendicular to a movement directionand a position of said mark relating to a direction substantiallyperpendicular to the movement direction; and correcting the positionaldeviation when said mask stage and said substrate stage aresynchronously moved, based on said measuring of positional deviation ofsaid mask stage, including said measuring of said position of said maskstage and said measuring of said position of said mark.
 8. A methodaccording to claim 7, wherein said mark is elongated along the movementdirection.
 9. An exposing apparatus synchronously moving a mask stagecarrying a mask having a predetermined pattern and a mark for ameasurement and a substrate stage carrying a substrate, to form thepattern image onto said substrate, comprising: a position measuringsystem for measuring a position of said mask stage along a directionsubstantially perpendicular to a movement direction; a mark detectingsystem for measuring a position of said mark; and a control system forobtaining a positional deviation of said mask stage along the directionsubstantially perpendicular to the movement direction based on theresult of the measurement of said mark detecting system and the resultof the measurement of said position measuring system, and for correctingthe positional deviation, and for synchronously moving said mask stageand said substrate stage.
 10. Apparatus for driving a mask stage usingan exposure device having said mask stage which mounts a mask formedwith a predetermined pattern and is movable in a predetermined scandirection, a movable mirror which is arranged on said mask stage and hasa reflection surface substantially parallel to the scan direction, saidreflection surface having an undesirable curvature, a measurement systemto measure a position, in a direction perpendicular to the scandirection, of said mask stage by radiating a measurement beam onto saidreflection surface, and a substrate stage which mounts a sensitivesubstrate, said exposure device being operative for exposing the patternon the mask onto the sensitive substrate while scanning said mask stagein the scan direction, said apparatus comprising a device connected tosaid mask stage that moves said mask stage in the directionperpendicular to the scan direction in accordance with said undesirablecurvature of said reflection surface so as to reduce an undesirableeffect on a pattern exposed onto the sensitive substrate, when said maskstage is scanned in the scan direction for an exposure.
 11. Apparatusfor aligning a mask on a mask stage as pre-processing for exposing apattern on a mask onto a sensitive substrate using an exposure devicehaving said mask stage which mounts the mask formed with said patternand is movable in a predetermined scan direction, and a substrate stagewhich mounts the sensitive substrate, said exposure device beingoperative for exposing the pattern on the mask onto the sensitivesubstrate while scanning said mask stage in the scan direction, saidapparatus comprising a device connected to said mask stage which rotatessaid mask stage by a predetermined rotational angle in a rotationaldirection without the mask mounted on the mask stage and which rotatessaid mask stage in a direction opposite to the rotational directionafter the mask is mounted on the mask stage.
 12. A scanning exposuremethod in which an exposure beam and an object are moved relatively in apredetermined direction during a scanning exposure, the methodcomprising: measuring information relating to a curvature of areflection surface which is substantially parallel to the predetermineddirection on a supporting member for supporting the object, thereflection surface being used for obtaining positional information ofthe supporting member; and controlling an operation, in which thesupporting member is used, based on the measured information.
 13. Ascanning exposure method according to claim 12, wherein the objectincludes a mask having a pattern.
 14. A scanning exposure methodaccording to claim 13, wherein the pattern of the mask is transferredonto a sensitive substrate and wherein movement of the supporting memberis controlled during the scanning exposure, based on said measuredinformation, such that undesirable distortion does not occur in apattern transferred on the sensitive substrate.
 15. A scanning exposuremethod according to claim 12, wherein the operation includes thescanning exposure.
 16. A scanning exposure method according to claim 12,wherein the operation includes a control of a position of the supportingmember during the scanning exposure.
 17. A scanning exposure methodaccording to claim 12, wherein the measuring is performed while saidsupporting member is moved in said predetermined direction.
 18. Ascanning exposure method according to claim 12, wherein the measuring isperformed by using a mark of the object supported by said supportingmember.
 19. A scanning exposure method according to claim 12, whereinthe measuring includes obtaining positional information of saidreflection surface in a direction perpendicular to said predetermineddirection at plural positions in said predetermined direction.
 20. Ascanning exposure method according to claim 19, wherein said positionalinformation of said reflection surface includes a deviation from areference position of said reflection surface in the directionperpendicular to said predetermined direction.
 21. A scanning exposuremethod according to claim 12, wherein said exposure beam includes light.22. A scanning exposure method according to claim 12, wherein saidreflection surface is used for obtaining positional information of saidsupporting member in a direction orthogonal to said predetermineddirection by using an interferometer.
 23. A scanning exposure methodaccording to claim 12, further comprising: detecting temperatureinformation of said supporting member to cope with a change in curvatureof said reflection surface based on the detecting.
 24. A method formanufacturing a device using a method according to claim
 12. 25. Amethod of making a scanning exposure apparatus in which an exposure beamand an object are moved relatively in a predetermined direction during ascanning exposure, the method comprising: providing a supporting memberwhich is movable in the predetermined direction while supporting theobject; providing a reflection surface which is substantially parallelto the predetermined direction on the supporting member and which isused for obtaining positional information of the supporting member; andproviding a measuring system which detects information relating to acurvature of the reflection surface.
 26. A method according to claim 25,wherein the object includes a mask having a pattern.
 27. A methodaccording to claim 25, wherein said measuring system includes aninterferometer for obtaining positional information of said supportingmember in a direction orthogonal to said predetermined direction byusing said reflection surface.
 28. A method according to claim 25,further comprising: providing a control system that is connected withthe supporting member and the measuring system and that controls anoperation, in which the supporting member is used, based on theinformation detected by the measuring system.
 29. A method according toclaim 28, wherein the operation includes a control of a position of thesupporting member during the scanning exposure.
 30. A method accordingto claim 25, wherein said supporting member has a first drivingmechanism for moving said object in said predetermined direction and asecond driving mechanism for fine moving said object in saidpredetermined direction, in a direction orthogonal to said predetermineddirection, and in a rotational direction.
 31. A method according toclaim 30, further comprising: providing a control system, connected withthe measuring system and the second driving mechanism, which controlsthe second driving mechanism based on the information detected by themeasuring system.
 32. A scanning exposure apparatus in which an exposurebeam and an object are moved relatively in a predetermined directionduring a scanning exposure, the apparatus comprising: a supportingmember which is movable in the predetermined direction while supportingthe object; a reflection surface which is substantially parallel to thepredetermined direction on the supporting member and which is used forobtaining positional information of the supporting member; and ameasuring system which detects information relating to a curvature ofthe reflection surface.
 33. A scanning exposure apparatus according toclaim 32, wherein the object includes a mask having a pattern.
 34. Ascanning exposure apparatus according to claim 32, wherein saidmeasuring system includes an interferometer for obtaining positionalinformation of said supporting member in a direction orthogonal to saidpredetermined direction by using said reflection surface.
 35. A scanningexposure apparatus according to claim 32, wherein said measuring systemincludes a mark sensor which detects a mark of the object supported bysaid supporting member.
 36. A scanning exposure apparatus according toclaim 32, further comprising: a control system that is connected withthe supporting member and the measuring system and that controls anoperation, in which the supporting member is used, based on theinformation detected by the measuring system.
 37. A scanning exposureapparatus according to claim 36, wherein the operation includes thescanning exposure.
 38. A scanning exposure apparatus according to claim36, wherein the operation includes a control of a position of thesupporting member during the scanning exposure.
 39. A scanning exposureapparatus according to claim 32, wherein said exposure beam includeslight.
 40. A scanning exposure apparatus according to claim 32, whereinsaid supporting member has a first driving mechanism for moving saidobject in said predetermined direction and a second driving mechanismfor fine moving said object in said predetermined direction, in adirection orthogonal to said predetermined direction, and in arotational direction.
 41. A scanning exposure apparatus according toclaim 40, further comprising: a control system, connected with themeasuring system and the second driving mechanism, which controls thesecond driving mechanism based on the information detected by themeasuring system.
 42. A scanning exposure apparatus according to claim33, further comprising: a corner cube type reflection member on thesupporting member; and an interferometer device, optically connectedwith said reflection member, which is used for obtaining positionalinformation of the supporting member in the predetermined direction. 43.A scanning exposure apparatus according to claim 33, further comprising:a plurality of interferometers, functionally associated with thesupporting member, which are used for obtaining positional informationof the supporting member in the predetermined direction.
 44. A scanningexposure apparatus according to claim 33, further comprising: atemperature sensor, connected with the supporting member, which is usedfor detecting a change in the curvature of the reflection surface.
 45. Ascanning exposure method comprising: moving an exposure beam and anobject relatively for a scanning exposure in a predetermined direction,the object being supported by a supporting member and a reflectionsurface being formed on the supporting member to obtain positionalinformation of the supporting member; and controlling a movement of thesupporting member, during the scanning exposure, based on informationrelating to a curvature of the reflection surface.
 46. A scanningexposure method according to claim 45, wherein the object includes amask having a pattern.
 47. A method according to claim 46, wherein thepattern of the mask is transferred onto a sensitive substrate andwherein movement of the supporting member is controlled during thescanning exposure, based on said measured information, such thatundesirable distortion does not occur in a pattern transferred on thesensitive substrates.
 48. A scanning exposure method according to claim45 further comprising: measuring the information relating to thecurvature of the reflection surface.
 49. A scanning exposure methodaccording to claim 48, wherein the measuring is performed while saidsupporting member is moved in said predetermined direction.
 50. Ascanning exposure method according to claim 48, wherein the measuring isperformed by using a mark of the object supported by said supportingmember.
 51. A scanning exposure method according to claim 48, whereinthe measuring includes obtaining positional information of saidreflection surface in a direction perpendicular to said predetermineddirection at plural positions in said predetermined direction.
 52. Ascanning exposure method according to claim 51, wherein said positionalinformation of said reflection surface includes a deviation from areference position of, said reflection surface in the directionperpendicular to said predetermined direction.
 53. A scanning exposuremethod according to claim 45, wherein the reflection surface issubstantially parallel to the predetermined direction on the supportingmember.
 54. A scanning exposure method according to claim 45, whereinsaid exposure beam includes light.
 55. A scanning exposure methodaccording to claim 45, wherein said reflection surface is used forobtaining positional information of said supporting member in adirection orthogonal to said predetermined direction by using aninterferometer.
 56. A scanning exposure method according to claim 45,further comprising: detecting temperature information of said supportingmember to respond to a change in curvature of said reflection surfacebased on the detecting.
 57. A method of making a scanning exposureapparatus in which an exposure beam and an object are moved relativelyin a predetermined direction during a scanning exposure, the methodcomprising: providing a supporting member which is movable in thepredetermined direction while supporting the object; providing areflection surface which is formed on the supporting member and which isused for obtaining positional information of the supporting memberduring the scanning exposure; and providing a control system,functionally associated with the supporting member, which controls amovement of the supporting member based on information relating to acurvature of the reflection surface.
 58. A method according to claim 57,wherein the object includes a mask having a pattern.
 59. A methodaccording to claim 57, further comprising: providing a measuring system,functionally connected with the control system, which detects theinformation relating to the curvature of the reflection surface.
 60. Amethod according to claim 59, wherein said measuring system includes aninterferometer for obtaining positional information of said supportingmember in a direction orthogonal to said predetermined direction byusing said reflection surface.
 61. A method according to claim 59,wherein the control system controls the movement of the supportingmember based on the information detected by the measuring system.
 62. Amethod according to claim 57, wherein the reflection surface issubstantially parallel to the predetermined direction on the supportingmember.
 63. A method according to claim 57, wherein said supportingmember has a first driving mechanism for moving said object in saidpredetermined direction and a second driving mechanism for fine movingsaid object in said predetermined direction, in a direction orthogonalto said predetermined direction, and in a rotational direction.
 64. Amethod according to claim 63, wherein the control system controls thesecond driving mechanism based on the information relating to thecurvature of the reflection surface.
 65. A scanning exposure apparatusin which an exposure beam and an object are moved relatively in apredetermined direction during a scanning exposure, the apparatuscomprising: a supporting member which is movable in the predetermineddirection while supporting the object; a reflection surface which isformed on the supporting member and which is used for obtainingpositional information of the supporting member during the scanningexposure; and a control system, functionally associated with thesupporting member which controls a movement of the supporting memberbased on information relating to a curvature of the reflection surface.66. A scanning exposure apparatus according to claim 65, wherein theobject includes a mask having a pattern.
 67. A scanning exposureapparatus according to claim 65, further comprising: a measuring system,functionally connected with the control system, which detects theinformation relating to the curvature of the reflection surface.
 68. Ascanning exposure apparatus according to claim 67, wherein saidmeasuring system includes an interferometer for obtaining positionalinformation of said supporting member in a direction orthogonal to saidpredetermined direction by using said reflection surface.
 69. A scanningexposure apparatus according to claim 67, wherein said measuring systemincludes a mark sensor which detects a mark of the object supported bysaid supporting member.
 70. A scanning exposure apparatus according toclaim 67, wherein the control system controls the movement of thesupporting member based on the information detected by the measuringsystem.
 71. A scanning exposure apparatus according to claim 65, whereinthe reflection surface is substantially parallel to the predetermineddirection on the supporting member.
 72. A scanning exposure apparatusaccording to claim 65, wherein said exposure beam includes light.
 73. Ascanning exposure apparatus according to claim 65, wherein saidsupporting member has a first driving mechanism for moving said objectin said predetermined direction and a second driving mechanism for finemoving said object in said predetermined direction, in a directionorthogonal to said predetermined direction, and in a rotationaldirection.
 74. A scanning exposure apparatus according to claim 73,wherein the control system controls the second driving mechanism basedon the information relating to the curvature of the reflection surface.75. A scanning exposure apparatus according to claim 65, furthercomprising: a corner cube type reflection member on the supportingmember; and an interferometer, optically connected with said reflectionmember, which is used for obtaining positional information of thesupporting member in the predetermined direction.
 76. A scanningexposure apparatus according to claim 65, further comprising: aplurality of interferometers, functionally associated with thesupporting member, which are used for obtaining positional informationof the supporting member in the predetermined direction.
 77. A scanningexposure apparatus according to claim 65, further comprising: atemperature sensor, connected with the supporting member, which is usedfor detecting a change in the curvature of the reflection surface.
 78. Ascanning exposure method in which an object is moved relative to anexposure beam during a scanning exposure, the method comprising: movinga stage in a moving direction prior to the scanning exposure, the objectbeing supported on the stage, a reflection surface being formed on thestage to obtain positional information of the stage and the reflectionsurface being substantially parallel to the moving direction; measuringpositional information of the stage in a direction crossing the movingdirection by applying a measuring beam of an interferometer to thereflection surface, during the movement of the stage prior to thescanning exposure; and controlling, during the scanning exposure,movement of the stage based on the measured positional information. 79.A method according to claim 78, wherein the positional informationmeasured by said interferometer prior to the scanning exposure changesin accordance with surface state of said reflection surface.
 80. Amethod according to claim 78, wherein said stage is moved along a guideupon moving in said moving direction.
 81. A scanning exposure methodaccording to claim 78, wherein the object is a mask having a pattern.82. A scanning exposure method in which a mask and a substrate are movedsynchronously relative to an exposure beam during a scanning exposure,the method comprising: moving a stage in a moving direction prior to thescanning exposure, the mask being supported on the stage, a reflectionsurface being formed on the stage to obtain positional information ofthe stage and the reflection surface being substantially parallel to themoving direction; measuring positional information of the stage in adirection crossing the moving direction by applying a measuring beam ofan interferometer to the reflection surface, during the movement of thestage prior to the scanning exposure; and adjusting, during the scanningexposure, positional relationship between the mask and the substratebased on the measured positional information.
 83. A method according toclaim 82, wherein the positional information measured by saidinterferometer prior to the scanning exposure changes in accordance withsurface state of said reflection surface.
 84. A method according toclaim 82, wherein the positional relationship between the mask and thesubstrate is adjusted based on the measured positional information suchthat undesirable distortion does not occur in a shot area formed on saidsubstrate by the scanning exposure.
 85. A method according to claim 82,wherein the positional relationship of the mask and the substrate isadjusted by controlling a position of the stage based on the measuredpositional information.
 86. A scanning exposure method according toclaim 82, wherein the interferometer has measuring axes perpendicular tothe moving direction.
 87. A microdevice manufacturing method includingan exposure process in which a mask and a substrate are moved inrespective scanning directions relative to an exposure beam during ascanning exposure in order to form a device pattern on the substrate,the method comprising: moving a stage in the scanning direction of themask prior to the scanning exposure, the mask being supported on thestage, a reflection surface being formed on the stage, and thereflection surface being substantially parallel to the scanningdirection of the mask; measuring positional information of the stage ina direction crossing the scanning direction by applying a measuring beamof an interferometer to the reflection surface, during the movement ofthe stage prior to the scanning exposure; and adjusting, during thescanning exposure, positional relationship between the mask and thesubstrate based on the measured positional information.
 88. A scanningexposure method in which an object is moved relative to an exposure beamin a scanning direction during an exposure, the method comprising:during the exposure, moving the object in the scanning direction byusing a first driving mechanism; during the exposure, measuring positionof the object by applying a measuring beam of an interferometer to areflection surface which is substantially parallel to the scanningdirection, the reflection surface being moved in the scanning directionrelative to the measuring beam; and during the exposure, moving theobject in a non-scanning direction perpendicular to the scanningdirection by using a second driving mechanism in order to compensate fora curvature of said reflection surface.
 89. A scanning exposure methodaccording to claim 88, wherein the second driving mechanism can finelymove the object in the scanning direction, the non-scanning direction,and in a rotational direction.
 90. A scanning exposure method accordingto claim 88, wherein the second driving mechanism includes a holdingmember which holds the object, and wherein the reflection surface isformed on the holding member.
 91. A scanning exposure method accordingto claim 90, further comprising: prior to the exposure, moving theholding member in the scanning direction, while applying the measuringbeam to the reflection surface, wherein the object is moved by using thesecond driving mechanism during the exposure, based on output of theinterferometer obtained by moving the holding member in the scanningdirection prior to the exposure.
 92. A scanning exposure methodaccording to claim 90, wherein the interferometer has measuring axesperpendicular to the scanning direction.
 93. A scanning exposure methodaccording to claim 88, further comprising: prior to the exposure,measuring information on the curvature of the reflection surface, andwherein during the exposure, the object is moved in the non-scanningdirection based on the measured information on the curvature.
 94. Ascanning exposure method according to claim 88, wherein the objectincludes a mask having a pattern.
 95. A scanning exposure method inwhich a mask and a substrate are moved in respective scanning directionsrelative to an exposure beam during an exposure, the method comprising:during the exposure, moving the mask in the scanning direction by usinga first driving mechanism; during the exposure, measuring position ofthe mask by applying a measuring beam of an interferometer to areflection surface extending substantially parallel to the scanningdirection, the reflection surface being moved in the scanning directionrelative to the measuring beam; and during the exposure, moving the maskby using a second driving mechanism in order to compensate for acurvature of said reflection surface.
 96. A scanning exposure methodaccording to claim 95, wherein the mask is moved in a directionperpendicular to the scanning direction by the second driving mechanism.97. A scanning exposure method according to claim 95, wherein the maskis moved using the second driving mechanism such that desirabledistortion does not occur in a shot area to be formed on the substrateby the scanning exposure.
 98. A scanning exposure method according toclaim 95, wherein the second driving mechanism can finely move theobject in the scanning direction, in a direction perpendicular to thescanning direction, and in a rotational direction.
 99. A scanningexposure method according to claim 95, wherein the second drivingmechanism includes a holding member which holds the mask, and whereinthe reflection surface is formed on the holding member.
 100. A scanningexposure method according to claim 99, further comprising: prior to theexposure, moving the holding member in the scanning direction, whileapplying the measuring beam to the reflections surface, wherein the maskis moved by using the second driving mechanism during the exposure,based on output of the interferometer obtained by moving the holdingmember in the scanning direction prior to the exposure.
 101. A scanningexposure method according to claim 99, wherein the interferometer hasmeasuring axes perpendicular to the scanning direction.
 102. A scanningexposure method according to claim 95, further comprising: prior to theexposure, measuring information on the curvature of the reflectionsurface, and wherein during the exposure, the mask is moved based on themeasured information on the curvature by using the second drivingmechanism.
 103. A microdevice manufacturing method including an exposureprocess in which a mask and a substrate are moved in respective scanningdirections relative to an exposure beam during a scanning exposure inorder to form a device pattern on the substrate, the method comprising:during the exposure, moving the mask in the scanning direction by usinga first driving mechanism; during the exposure, measuring position ofthe mask by applying a measuring beam of an interferometer to areflection surface extending substantially parallel to the scanningdirection, the reflection surface being moved in the scanning directionrelative to the measuring beam; and during the exposure, moving the maskby using a second driving mechanism in order to compensate for acurvature of said reflection surface.
 104. A method of making a scanningexposure device that is operative for exposing a pattern on a mask ontoa sensitive substrate, comprising: providing a mask stage that ismovable in a predetermined scan direction and on which a mask formedwith a predetermined pattern is mountable; providing a movable mirrorthat is arranged on said mask stage and that has a reflection surfacesubstantially parallel to the scan direction, said reflections surfacehaving an undesirable curvature; providing a measurement system tomeasure a position, in a direction perpendicular to the scan direction,of said mask stage by radiating a measurement beam onto said reflectionsurface; providing a substrate state on which a sensitive substrate ismountable; and providing a driver to move said mask stage in a directionperpendicular to the scan direction in accordance with said undesirablecurvature of said reflection surface so as to reduce an undesirableeffect on a pattern exposed onto the sensitive substrate, when said maskstage is scanned in the scan direction for an exposure.
 105. A method ofmanufacturing a semiconductor device that employs a sensitive substrate,using an exposure device having a mask stage which mounts a mask that isformed with a predetermined pattern and is movable in a predeterminedscan direction, a movable mirror which is arranged on said mask stageand has a reflection surface substantially parallel to the scandirection, said reflection surface having an undesirable curvature, ameasurement system to measure a position, in a direction perpendicularto the scan direction, of said mask stage by radiating a measurementbeam onto said reflection surface, and a substrate stage which mountssaid sensitive substrate, said exposure device being operative forexposing the pattern on the mask onto the sensitive substrate whilescanning said mask stage in the scan direction, said method including:placing the mask on said mask stage; and moving said mask stage in adirection perpendicular to the scan direction in accordance with saidundesirable curvature of said reflection surface so as to reduce anundesirable effect on a pattern exposed onto the sensitive substrate,when said mask stage is scanned in the scan direction for an exposure.